When performing a hydrostatic test of a plumbing system, it is necessary to isolate the plumbing system. U.S. Pat. No. 6,575,475 (Duncan) entitled “Tear-out rubber coupling” describes a coupling capable of holding two section of pipe in end to end relation with a removable barrier formed with a cylindrical section of rubber disposed in between. There are millions of couplings capable of holding two sections of pipe in end to end relation that are sold annually. What is required is a test barrier that is capable of being used with these existing pipe couplings.